An example of a sighting instrument of the type to which the present invention relates is described in U.S. Pat. No. 3,942,901. A commercial implementation of the same is the Mark V sight available from Action Arms. That device comprises an electronic light dot reticle sight of relatively simple, lightweight construction that enables rapid and precise aiming of a firearm, even under low light conditions. The sight is of double-barreled side-by-side construction, with a tubular battery or circuitry housing supported by a brace or strut in spaced position adjacent a firearm mountable tubular lens housing.
The lens housing has front and rear apertures and contains a lens system having a rearwardly facing concave light reflecting surface that serves as a semi-transparent mirror to produce an image of a small electric light source. The semi-transparent mirror surface and the light source are arranged so that a dot point image will be perceived ahead of the mirror surface by an observer looking through the sight, to act as a sighting mark between the observer's eye and the target. The lens system is mounted in a tube supported within an angled channel of a rubber ring mounted in the lens housing. Vertical and horizontal positioning screws that contact the tube at points away from the ring, provide elevation and cross-angle or windage adjustment control for the sight by positioning the dot point image relative to the lens housing axis. The adjustment screws are marked in minute-of-angle increments, are coin turnable, and are shielded by protective dust covers. The angle of the channel causes the ring to bias the lens system tube against the dot positioning action of the screws.
The battery or circuitry housing has a removable cover at one end for replacement of two mercury cells that power the light source located in the lens housing. An on/off switch and intensity control for the light (and thus the dot image sighting mark) are provided at the other end of the battery housing in the form of a rotating knob rheostat. The lens housing is provided with strap brackets for mounting on a firearm, and the battery housing is joined in spaced position alongside the lens housing by a radially-directed supporting brace or strut. Electrical connection between the rheostat and power source in the battery housing and the light in the lens housing is established by wires running through the brace.
In a typical conventional configuration for a right-handed or right aiming shooter, the battery housing is located to the left of and slightly below the lens housing, with its longitudinal axis in the third quadrant at an angle of about 210 degrees of circle running counterclockwise about a center on the longitudinal axis of the lens housing. Because of the housing placement and adjustment control arrangements of conventional optical sighting instruments of this type, separate embodiments are required for the left-handed or left-aiming shooter, or where firearm construction requires placement of the battery housing to the right of the lens housing.